Methods for manufacturing a clip and clip

ABSTRACT

The present invention relates to a method of making clips which can be used to engage body tissue for the purpose of closing wounds. Such clips are generally annular in shape and have radially inwardly extending tines. The present invention first forms a precursor which, in one embodiment, has the tines extending radially outwardly from the annular body and then forms the clip by inverting the precursor such that the tines extend radially inwardly. In an alternate embodiment, the precursor is formed with an over-sized lateral dimension and then compressed inwardly to bring the tines closer A together and to reduce the lateral dimension of the precursor. It is preferred to manufacture such clips from a superelastic alloy such as nickel-titanium, in which case the inverted or compressed precursor must be heated and quenched to heat set the clip in its final shape.

FIELD OF INVENTION

The use of certain types of clips, which are initially generally planarand which are deformed to non-planar configuration prior to use, toclose openings through tissue, e.g., into body lumens, and moreparticularly to close a puncture made to gain access to a blood vesselor other body lumen is known. Such clips are generally annular and havetines extending radially from an annular body. For example, such clipsare disclosed in the aforementioned co-pending applications and inpublished PCT Applications WO/99/62408, WO/00/56223 and WO/00/56227, thedisclosures of which are incorporated by reference herein. Variousmethods, e.g., stamping, laser cutting, chemical etching and the likehave been used to form the clips from a sheet of metal. Conventionalmanufacturing methods are limited with regard to minimizing the spacebetween the tines because the necessary manufacturing tolerances requirethat sufficient space be allowed for the manufacturing tools and/orprocessing materials. Improved methods of manufacturing these types ofclips and the clips resulting from them would make such clips moreeffective for many such uses.

SUMMARY OF THE INVENTION

The present invention is directed to methods for manufacturing tissueengaging clips in a manner in which a clip-precursor is first formed andsuch precursor is then reconfigured into the final shape of the clip. Ina preferred embodiment of the invention, a clip having an annular orhoop-shaped generally planar configuration with radially inwardlyextending tines is manufactured by first forming a precursor with thetines extending radially outward and then reconfigured by inserting theprecursor to its final shape with the tines extending radially inwardand then heat setting the clip in this configuration. This permits thetines to be packed more closely together which enhances the sealingfunction of the clip and reduces the size of the clip's footprint. Aswill be explained in more detail herein, this manufacturing methodovercomes the limitations of conventional methods in which the clip ismanufactured in its final configuration.

In another preferred embodiment, an annular or hoop-shaped planar clipprecursor with radially inwardly extending tines is first manufacturedin an oversize configuration and then has its lateral dimensions reducedto pack the tines closer together and to reduce the footprint of theclip and then heat set in that configuration.

DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate the before and after configuration of a clipmanufactured according to one embodiment of this invention.

FIGS. 2A AND 2B illustrate the before and after-configuration of a clipmanufactured according to another embodiment of the invention.

FIGS. 3A-3C illustrate alternate before and after-configurations ofclips manufactured according to the method of this invention in whichthe before configuration is that of FIG. 2A.

FIG. 4 illustrates a clip which, while generally planar, has tines whichextend radially inwardly at an angle to the plane defined by the body.

FIGS. 5 and 6 illustrate clip precursors in which radially opposedprimary tines have different lengths.

FIG. 7 illustrates the preferred relationship between the grainorientation of a nitinol sheet and the primary tines of a clipprecursor.

DETAILED DESCRIPTION OF THE INVENTION

The clips manufactured according to the present invention are useful forengaging tissue so as to connect tissue segments together or to closeand/or seal openings through tissue such as a puncture wound in a bodylumen. These clips may be used by deforming them from their generallyplanar configuration such that the tines are pointing in a directiongenerally transverse to the plane, holding the clip in this deformedcondition, deploying the clip proximal to the tissue to be engaged andremoving the deforming force such that the clip engages the tissue andattempts to return to its original generally planar configuration. Themethods and apparatus disclosed in the above-mentioned U.S. patentapplication Ser. Nos. 10/081,726 and 09/732,178 can be used to deploythe clips of the present invention to engage tissue and close or seal anopening.

In such use, the deformation of the clip causes the tines to be directedgenerally axially away from the body of the clip and it is the elasticproperty of the deformed clip which causes it to attempt to return toits original generally planar configuration. The body of the device maycomprise a series of looped elements which generally define an endlesszigzag pattern, e.g., a sinusoidal pattern, extending about a centralaccess. The looped elements are believed to facilitate deforming thedevice between the planar and transverse configurations, e.g., bydistributing stresses through the device and minimizing localizedstresses in the curved regions.

In a first preferred embodiment of the present invention, a clipprecursor is first formed from a sheet of material, preferably asuperelastic alloy, such as a nickel-titanium alloy (“Nitinol”) alloy.The property of superelasticity and of certain alloys which possess thatproperty is disclosed in U.S. Pat. No. 4,665,906 which is incorporatedby reference herein. This forming can be done by removing portions ofthe material by cutting, chemical etching, laser cutting, photochemicaletching, stamping, electrical discharge machining and the like toproduce a precursor such as that shown in FIG. 1A which has radiallyoutward extending tines. The precursor can then be polished using one ormore processes such as electropolishing, tumbling, sand blasting,sanding and the like or such polishing can be done as a final step afterthe clip is formed. Forming of a precursor in this manner does notrequire working to tolerances as close as those which would be requiredif the clip was to be manufactured in its final configuration shown inFIG. 1B because the radially outwardly extending tines of the precursorshown in FIG. 1A are easily accessible by the forming tool whereasattempting to directly form the clip with radially inwardly extendingtines which are closely spaced requires difficult high precision metalcutting. Thus, manufacture of a precursor which is then reconfigured tofinal clip shape permits the achievement of closer spacing between theelements of the final clip than would otherwise be achievable withconventional methods.

The precursor 10 comprises a hoop-shaped planar body 11 which hasoutwardly extending primary (longer) tines 12 and secondary (shorter)tines 13. For example, the primary trials may be 0.070 to 0.105 inchesin length and the secondary tines may be 0.025 to 0.035 inches inlength. Each of the tines terminates in a point 14. When the precursor10 has been reconfigured into clip 16 shown in FIG. 1B, the tines 12 and13 become the tissue engaging portions of the clip. The tines may besharpened or given a shape, e.g., barbs (not shown), while the device isin the precursor state. The body 11 may compromise connecting links suchas loops 15. These links may have any suitable shape provided that suchshape does not interfere with inversion of the precursor 10.

The precursor 10 is then inverted to reconfigure it into the shape ofclip 16. In this preferred embodiment in which the precursor is formedfrom a sheet of nickel-titanium alloy, the inverted precursor is thenheat set, e.g., by heating to a temperature of 510° C., and thenquenched to cool to room temperature. The clip 16 will now be in theaustenitic state.

Heat setting and quenching are essential to successful practice of theinvention with superelastic alloys. As explained in more detail in U.S.Pat. No. 4,665,906, a superelastic alloy such as nickel-titanium existsin two states, the austenitic state and the martensitic state; Suchalloys will initially be in the austenitic state, e.g., when theprecursor is formed. However, when the precursor is inverted to take theshape of the final clip, the stress experienced by the alloy during theinversion will cause the alloy to be partially or wholly converted tothe martensitic state. Such a martensitic state is commonly referred toas stress-induced martensite. Such martensite structure has the propertyof superelasticity and the inverted precursor would revert to itsoriginal shape if not held in the inverted configuration.

Since, if the inverted precursor was left in the martensitic state, itwould want to elastically revert to its original uninverted state, itmust be converted back to austenite. Thus, heating and quenching arerequired to convert the inverted precursor from the martensitic state tothe austenitic state such that the clip is stable in its planarconfiguration as shown in FIG. 1B and will retain that configuration.

The times and temperatures for heat setting of superelastic alloys ofvarious compositions can be determined from existing literature or canbe determined empirically without any difficulty. The clips are small insize and the heating and quenching may be done with any conventionalheating and quenching equipment. For example, once inverted, theinverted precursor can be held in that configuration and placed in afixture which will hold it in the inverted configuration during heatsetting.

When clips are manufactured according to the present invention, thespace between the tines may actually be eliminated, i.e., afterinverting the precursor, the tines may be in contact with each other, ineither a side-by-side or an over-and-under relationship. The number,length and spacing of the tines may be varied according to the desiresof the manufacturer. Furthermore, while use of a planar precursor is aconvenience in manufacturing, a planar configuration is not required.For example, the precursor could be bent along a diameter or major orminor axis of the precursor and could be heat set in such a bentconfiguration. Alternatively, the clip, while generally planar, may havethe tines extending at an acute angle to the plane defined by the bodyas shown in FIG. 4 in which the body 11 and tines 12 are shown.Furthermore, manufacturing from a sheet of material is a convenience,but other manufacturing techniques, including joining of components suchas the tines to the body, can be accomplished by welding, brazing, orother known methods of joining materials. In such cases, one or more ofsuch components may be circular in cross-section or tubular inconfiguration.

Still further, the clip need not be fabricated from a single material,e.g., the tines may be manufactured from a different material than thebody. In such cases, a portion of the clip such as the tines may bebioabsorbable provided that the final clip is capable of elasticrecovery after being deformed. An advantage of the present invention isthat it permits the production of clips with tines that are 30 to 40% ormore longer than those which could be made with prior direct cuttingmethods, because there is no limit on the length of the tine which isformed on the precursor. Thus, after the precursor is inverted, thetines may overlap the annular body.

In the alternative embodiment of this invention illustrated in FIGS. 2Aand 2B, the precursor 20 is manufactured in an expanded oversizeconfiguration to provide space for removing material from a sheet ofmaterial, preferably a superelastic alloy such as nickel-titanium, byconventional methods such as cutting, chemical etching, photochemicaletching, stamping, electric discharge machining, laser cutting or thelike.

The precursor 20 is reconfigured by imposing radially inwardly directedforce on body 21 such that precursor 20 takes a smaller planar shapesuch as one of those shown in FIG. 2B. The precursor 20 has a planarbody 21, tines 22 and 23 having points 24 and such tines are connectedby links 25 as previously described with regard to FIG. 1A. Thereconfigured precursor is then heat set and quenched as described aboveto complete the manufacture of clip 26.

Clips of still other configurations can be manufactured in the manner ofclip 26 by starting with a differently shaped precursor such asprecursor 30 shown in FIG. 3A. Precursor 30 can be reconfigured by beingsubjected to radially inward deforming forces as shown in FIG. 3B or byopposed laterally inward forces as shown in FIG. 3C. In each case, theplanar body 31 having tines 32 and 33 with points 34 and links 35 willbe caused to take a smaller dimension and will be heat set as describedabove to form clips 36 and 37. Clips manufactured according to themethod of the present invention can have a multitude of configurationsother than those shown in FIGS. 1B, 2B, and 3C and 3D. For example, theconfigurations shown in U.S. patent applications Ser. Nos. 09/732,178and 10/081,726 could be manufactured according to the present invention.

It has been found that nitinol sheet is stronger in one direction thanin others, which may be the result of crystal orientation in thenitinol. It is preferred to form the clip precursors such that theprimary tines are aligned with the strongest orientation of the nitinol.It has been found, as shown in FIG. 7, that the greatest strength of theprimary tines is achieved if those tines are transverse to the grainorientation of the nitinol. Thus, FIG. 7 illustrates clip precursor 60having primary tines 61 as the precursor would be cut from sheet 62. Thegrain orientation of sheet 62 is shown by the double-headed arrow 63.Typically, a plurality of precursors 60 would be cut from the samesheet, each with its primary tines transverse to the grain orientationof the sheet. In addition, even if clips are formed directly withoutusing precursors, it is desirable that their primary tines be transverseto the grain orientation.

The clips of the present invention may have primary or secondary tineswhich have the same or different lengths and the tines may be straightor curved. For example, radially opposed tines may have one tine at “12o'clock” which is longer than the opposing tine at “6 o'clock.”Exemplary configurations of clip precursors with primary tines ofdifferent length are shown in FIGS. 5 and 6. In FIG. 5, clip precursor40 is shown with a primary tine 41 which is shorter than primary tine42. Similarly, in FIG. 6, a clip precursor is shown which has a primarytine 51 which is shorter than primary tine 52.

The clips of the present invention may also be delivered using theapparatus and methods described in U.S. patent application Ser. No.10/081,273, filed Feb. 21, 2002 which is assigned to the assignee of thepresent application and the disclosure of which is incorporated byreference herein. Similarly, the apparatus and methods disclosed in U.S.patent application Ser. No. 10/081,717, filed Feb. 21, 2002, which isassigned to the Assignee of the present application and the disclosureof which is incorporated by reference herein, may be used.

Other features can be added to the clips including radio-opaque markers,and/or porous surfaces to promote tissue ingrowth or the clip may becoated in whole or in part with a bioabsorbable material and/or coatedwith a material containing a substance which is delivered to the patientfor therapeutic, diagnostic or other purposes. Such coatings maycomprise peptides, clotting factors or other materials designed tobenefit the patient.

While the principal object of the present invention is to provide amanufacturing method which facilitates the production of clips having asmall footprint, the present invention can also be used to make clips oflarger dimensions since, no matter what methods are used to cut theprecursor from a sheet of material, the ease of manufacture of evenlarger size clips is facilitated. Thus, the advantages of the presentinvention may be realized with regard to clips having larger sizes andclips having a variety of configurations.

Having fully described the present invention including a description ofpreferred embodiments, it is to be understood that the scope of thisinvention is not to be limited to those preferred embodiments, but is ofthe full scope of the appended claims.

1. A method of manufacturing a clip comprising the steps of: forming theprecursor of a clip from a material comprising a superelastic alloywhich has an austenitic state and a martensitic state, said precursorhaving a generally annular body which is generally planar and having oneor more tines which extend radially outwardly from said body; invertingsaid precursor such that said tines extend radially inwardly; heatingsaid precursor in its inverted configuration to cause said alloy tobecome substantially austenitic; and quenching said heated precursor toform a clip which is substantially austenitic.
 2. The method of claim 1wherein said alloy is nickel-titanium.
 3. The method of claim 1 whereinsaid body comprises a plurality of looped elements.
 4. The method ofclaim 1 wherein, after inversion, at least two tines are in side-by-siderelationship.
 5. The method of claim 1 wherein, after inversion, atleast two tines are in over-and-under relationship.
 6. The method ofclaim 1 wherein at least one tine is longer than a radially opposedtine.
 7. The method of claim 1 wherein said forming step comprisescutting said precursor from a sheet of material comprising asuperelastic alloy.
 8. A method of manufacturing a clip comprising thesteps of: forming the precursor of a clip from a material comprising asuperelastic alloy which has an austenitic state and a martensiticstate, said precursor having a generally annular body which is generallyplanar and having one or more tines which extend radially inwardly fromsaid body; said precursor having a lateral dimension which issubstantially larger than that of the clip; compressing said precursor ma radially inward direction to bring said tines substantially closertogether; heating said precursor in its compressed configuration tocause said alloy to become substantially austenitic; and quenching saidheated precursor to form a clip which is substantially austenitic. 9.The method of claim 8 wherein said alloy is nickel titanium.
 10. Themethod of claim 8 wherein said body comprises a plurality of loopedelements.
 11. The method of claim 9 wherein the nickel titanium has agrain orientation and at least two tines have a longitudinal dimensiontransverse to the grain orientation.
 12. The method of claim 8 wherein,after compression, at least two tines are in side-by-side relationship.13. The method of claim 1 wherein, after compression, at least two tinesare in over-and-under relationship.
 14. A clip manufactured according tothe method of claim
 1. 15. A clip manufactured according to the methodof claim
 6. 16. A clip manufactured according to the method of claim 8.